This investigation will include the construction of physical and deletion maps of the human chromosomal region 11p11.p12. Overlapping YACS and cosmids will be identified through the construction of a physical map. The deletion map will allow definition of a minimal region of chromosomal loss in patients with multiple exostoses and possibly with parietal foramina and/or mental retardation. Cosmids identified through the physical mapping effort will be used to perform exon trapping and identify candidate genes potentially involved in a contiguous gene deletion syndrome that includes multiple exostoses. All candidate genes will be analyzed for a potential role in multiple exostoses. It is also possible that this work will result in the identification of genes involved in other associated, but unrelated, traits such as parietal foramina or mental retardation.